This invention relates to a device for assembling an integrated electron gun system for a color display tube of the "in-line" type which is composed of a number of electrodes centered around an axis. The device comprises centering pins situated with their longitudinal axes substantially in one plane, on which pins the electrodes are positioned and are then fixed mechanically with respect to each other.
The invention also relates to a method of assembling an integrated electron gun system for a color display tube of the "in-line" type by means of such a device.
A device for assembling an electron gun system which comprises three individual electron guns built up from electrodes is disclosed in U.S. Pat. No. 3,906,279. The device comprises a base on which three centering pins are connected. The axes of the pins are parallel to each other and are situated in one plane. The diameters of the pins becomes smaller stepwise towards the free ends of the pins. The electrodes are centered around the pins with the interposition of spacer plates which fix the spacings between the electrodes. The surface of the base is used as a reference surface. After positioning all the electrodes around the centering pins, the electrodes comprising connection braces are sealed in glass supporting rods by means of the braces. The three electron guns then form one assembly. The electron gun system is then slid from the centering pins.
An electron gun system of the integrated type for an "in-line" color display tube is described in Netherlands Patent Application No. 8203322, corresponding to U.S. patent application Ser. No. 516,016 filed July 22, 1983, and which may be considered to be incorporated herein by reference. In such an integrated electron gun system most gun electrodes are common to all the three electron guns. The common electrodes usually comprise a metal plate which has three apertures which may have collars and which serve to pass the three electron beams. The plate usually constitutes the bottom of a cup-shaped electrode component.
A device for assembling such an integrated electron gun system usually comprises two centering pins on which the outermost apertures of the electrodes are centered. The diameter of said centering pins depends on the tolerances of the diameter of the aperture in the electrode components to be assembled, the tolerances in the distance between the apertures in an electrode component and the desired play between the diameter of the aperture and centering pin diameter in behalf of the capability of detaching the assembled electron gun system from the centering pins.
The disadvantage of such a device for assembling the electron gun is that a number of alignment errors may be made such as centering errors of the apertures and obliguity errors of the lens components in which the apertures are provided. Such alignment errors are not permitted in electron gun systems in which a strong lens is introduced into the triode part. The triode part of an electron gun is the part comprising the cathode, the control grid and the first anode.
Such an electron gun system is disclosed in Netherlands Patent Application No. 8204185, corresponding to allowed U.S. patent application Ser. No. 544,169 filed Oct. 21, 1983, and which may be considered to be incorporated herein by reference. The result of such a strong lens is that the alignment errors result in comparatively large beam displacing errors (these are errors in the location and direction of the beam) as compared with known electron guns.